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/*!

    \class QDesignerTaskMenuExtension

    \brief The QDesignerTaskMenuExtension class allows you to add custom

    menu entries to Qt Designer's task menu.

    \inmodule QtDesigner

    QDesignerTaskMenuExtension provides an interface for creating

    custom task menu extensions. It is typically used to create task

    menu entries that are specific to a plugin in \QD.

    \QD uses the QDesignerTaskMenuExtension to feed its task

    menu. Whenever a task menu is requested, \QD will query

    for the selected widget's task menu extension.

    \image taskmenuextension-example-faded.png

    A task menu extension is a collection of QActions. The actions

    appear as entries in the task menu when the plugin with the

    specified extension is selected. The image above shows the custom

    \gui {Edit State...} action which appears in addition to \QD's

    default task menu entries: \gui Cut, \gui Copy, \gui Paste etc.

    To create a custom task menu extension, your extension class must

    inherit from both QObject and QDesignerTaskMenuExtension. For

    example:

    \snippet doc/src/snippets/code/doc_src_qtdesigner.qdoc 9

    Since we are implementing an interface, we must ensure that it

    is made known to the meta-object system using the Q_INTERFACES()

    macro. This enables \QD to use the qobject_cast() function to

    query for supported interfaces using nothing but a QObject

    pointer.

    You must reimplement the taskActions() function to return a list

    of actions that will be included in \QD task menu. Optionally, you

    can reimplement the preferredEditAction() function to set the

    action that is invoked when selecting your plugin and pressing

    \key F2. The preferred edit action must be one of the actions

    returned by taskActions() and, if it's not defined, pressing the

    \key F2 key will simply be ignored.

    In \QD, extensions are not created until they are required. A

    task menu extension, for example, is created when you click the

    right mouse button over a widget in \QD's workspace. For that

    reason you must also construct an extension factory, using either

    QExtensionFactory or a subclass, and register it using \QD's

    \l {QExtensionManager}{extension manager}.

    When a task menu extension is required, \QD's \l

    {QExtensionManager}{extension manager} will run through all its

    registered factories calling QExtensionFactory::createExtension()

    for each until it finds one that is able to create a task menu

    extension for the selected widget. This factory will then make an

    instance of the extension.

    There are four available types of extensions in \QD:

    QDesignerContainerExtension, QDesignerMemberSheetExtension,

    QDesignerPropertySheetExtension, and QDesignerTaskMenuExtension.

    \QD's behavior is the same whether the requested extension is

    associated with a container, a member sheet, a property sheet or a

    task menu.

    The QExtensionFactory class provides a standard extension factory,

    and can also be used as an interface for custom extension

    factories. You can either create a new QExtensionFactory and

    reimplement the QExtensionFactory::createExtension() function. For

    example:

    \snippet doc/src/snippets/code/doc_src_qtdesigner.qdoc 10

    Or you can use an existing factory, expanding the

    QExtensionFactory::createExtension() function to make the factory

    able to create a task menu extension as well. For example:

    \snippet doc/src/snippets/code/doc_src_qtdesigner.qdoc 11

    For a complete example using the QDesignerTaskMenuExtension class,

    see the \l {designer/taskmenuextension}{Task Menu Extension

    example}. The example shows how to create a custom widget plugin

    for \QD, and how to to use the QDesignerTaskMenuExtension

    class to add custom items to \QD's task menu.

    \sa QExtensionFactory, QExtensionManager, {Creating Custom Widget

    Extensions}

*/

/*!

    \fn QDesignerTaskMenuExtension::~QDesignerTaskMenuExtension()

    Destroys the task menu extension.

*/

/*!

    \fn QAction *QDesignerTaskMenuExtension::preferredEditAction() const

    Returns the action that is invoked when selecting a plugin with

    the specified extension and pressing \key F2.

    The action must be one of the actions returned by taskActions().

*/

/*!

    \fn QList<QAction*> QDesignerTaskMenuExtension::taskActions() const

    Returns the task menu extension as a list of actions which will be

    included in \QD's task menu when a plugin with the specified

    extension is selected.

    The function must be reimplemented to add actions to the list.

*/